Sunni Ali was the ruler of the Songhai Empire of the west Africa from 1465 to 1492. This dynasty was known to have its wide range of army that captured and fortified Timbuktu and Djenne. He conducted repressive policies against the scholars of Timbuktu, particularly in the Sankore region, with which he expelled to gain control of the town that Tuareg was handling. This was the time that a fleet patrolled the Niger River which lead to the surpassing of Mali Empire.
Byzantine empire continued in the East after the fall of the Western Roman Empire.
The main function of the introductory word in sentence 2 would be that "<span>It is a transition word," since it helps show the time in which this event is taking place (at the same time, that is). </span>
